热硫化硅橡胶海绵发泡技术的研究

研究了热硫化硅橡胶的化学发泡技术和发泡工艺条件,对影响发泡效果和开孔率的因素进行了分析。结果表明,在硅橡胶化学发泡中,需采用预发泡工艺使硫化和发泡速度相匹配,在预发泡中,预发泡时间在１５０～１９０ｓ范围内,塑性值为０．６时发泡效果较好;硅橡胶在较低温度下化学发泡成型时开孔率较低,发泡温度升高,开孔率上升。     

AC发泡剂在橡胶型CM中的应用

利用发泡流变仪研究了CM的硫化条件和硫化特性,得出硫化交联反应速度V、硫化指数CCRI和表观活化能E;同时研究了助交联剂TAIC以及工艺条件对发泡橡胶性能的影响。结果表明:添加助交联剂TAIC发泡试样的硫化交联反应速度V加快,硫化指数CCRI和交联反应活化能E变大;添加助交联剂TAIC发泡试样在保持低密度的同时,获得较高的机械强度,综合发泡性能好;充模质量对发泡行为影响大,33 g充模的胶料综合发泡性能好;170℃时,10 MPa压力下硫化会得到综合性能较好的发泡效果。     

预硫化工艺对三元乙丙橡胶发泡材料性能的影响

研究预硫化温度和时间对三元乙丙橡胶(EPDM)发泡材料结构和性能的影响。结果表明:预硫化温度为110℃时,EPDM发泡材料的硫化速度和发泡速度匹配较佳;随着预硫化温度的升高,EPDM发泡材料的泡孔孔径增大,泡孔数目减小;在110℃预硫化温度下,随着预硫化时间的延长,EPDM发泡材料的泡孔孔径减小,泡孔数目增大,且邵尔C型硬度和拉伸强度提高,静刚度和动静刚度比降低。     

用硫化与发泡分步法制备均孔三元乙丙橡胶泡沫

采用辐射硫化技术制备了三元乙丙橡胶泡沫,使硫化与发泡分步进行,避免了传统发泡过程中硫化速率与发泡速率难以匹配的问题。研究了发泡条件对三元乙丙橡胶泡沫密度的影响,探讨了吸收剂量和发泡剂用量对制品结构与性能的影响规律,并用扫描电镜观察了泡孔形态。结果表明,发泡温度为175℃、发泡时间为4 min、吸收剂量为20 kGy及发泡剂用量为6份(质量)时三元乙丙橡胶泡沫的泡孔比较均匀,力学性能良好。     

助交联剂对过氧化物硫化HNBR性能的影响

考察了三羟甲基丙烷三甲基丙烯酸酯(SR350)、三羟甲基丙烷三丙烯酸酯(SR351)作为过氧化物的助交联剂对氢化丁腈橡胶(HNBR)的硫化特性、加工性能、物理机械性能及老化性能的影响,并采用无转子流化仪研究了2种助交联剂的硫化反应动力学。结果表明,添加助交联剂的胶料的门尼粘度下降,硫化程度都有所增加,压缩永久变形性能改善,并且老化后性能保持率变好。其中添加SR351的试样的硫化程度较高,加工性能和压缩永久形变更佳。而助交联剂的存在提高了硫化反应的活化能,加入SR350和SR351胶料的活化能分别为154.76kJ/mol和158.78kJ/mol,表明加入助交联剂的硫化反应速率对温度的依赖性更大。     

NR硫化返原动力学研究

依据ＮＲ硫化返原机理，提出了硫化返原动力学模型。用该模型对硫化曲线进行计算机模拟，可求出各反应速率常数，并能得到多硫键、双硫键和单硫键以及断裂交联键的浓度与硫化时间的函数关系。计算机模拟结果表明，由该模型得到的不同硫化温度下的模拟硫化曲线与实际硫化曲线相吻合，求出的各反应速率常数与硫化温度的关系符合Ａｒｈｅｎｉｕｓ方程。分解反应的活化能大于脱硫反应的活化能可以解释硫化温度越高，硫化返原程度越大     

发泡体系和硫化体系对NBR海绵性能的影响

探讨发泡体系、硫化体系以及混炼胶门尼粘度和硫化条件对NBR海绵性能的影响。结果表明,采用硫黄/硫化剂DTDM/促进剂CZ/DM/PZ/ZBX硫化体系与发泡剂H/OBSH/BK-1/碳酸氢铵水溶液/尿素发泡体系配合,混炼胶的门尼粘度[ML(1+4)100℃]控制为45~60,硫化条件为170℃×8 min时,胶料的硫化速度与发泡速度匹配,海绵的闭孔率大,泡孔极小且分布均匀,表面光滑,表观密度和压缩永久变形较小。     

二段硫化条件对均聚氯醚橡胶(CO)性能的影响

研究了二段硫化条件(硫化温度和硫化时间)对均聚氯醚橡胶(CO)基本性能和压缩永久变形性能的影响。结果表明,二段硫化温度越高,硫化时间越长,胶料的拉伸强度和定伸应力越大,硬度越高;而撕裂强度、伸长率、拉断永久变形以及压缩永久变形越小,其中胶料的硬度、拉伸强度、伸长率、压缩永久变形在一定时间后基本上趋于平衡,较好的二段硫化条件为150℃～160℃×3～4h。     

硫化体系对再生胶发泡性能的影响

采用跳模法对再生胶进行发泡,考察了硫黄、促进剂CZ、TMTD对再生胶发泡特性及发泡体物理机械性能的影响,并用体视显微镜表征了泡孔结构。结果表明,随着硫黄用量的增加,再生胶发泡体的密度增大,发泡率、收缩率、泡孔体积分数及泡孔直径均减小,邵尔C硬度和压缩强度增大;随着CZ用量的增加,再生胶发泡体的密度和泡孔直径减小,发泡率和泡孔体积分数先减小后增大,收缩率先增大后减小,压缩强度和邵尔C硬度均先减小后增大;随着TMTD用量的增加,再生胶发泡体的密度增大,发泡率和泡孔体积分数均减小,收缩率和泡孔直径先增大后减小,压缩强度增大后略有下降。     

BPA发泡点分析仪的测试理论和计算式

BPA发泡点分析仪是研究橡胶硫化发泡特性的仪器。BPA发泡点分析仪依据无界薄板热传导计算式表征硫化试样任一位置温度和热扩散系数;依据阿累尼乌斯公式,通过列表法和绘图法表征胶料的硫化活化能、等效硫化时间和发泡时间。     

硫化工艺对EPDM微孔橡胶垫板动静刚度比的影响

研究了硫化三要素及填胶量对EPDM微孔橡胶垫板动静刚度比的影响。结果表明,硫化温度、硫化时间以及硫化压力对橡胶垫板动静刚度比的影响是通过橡胶发泡倍率的变化来体现的,即发泡倍率越大,动静刚度比越小;密度相当时,孔径越小且孔壁越薄,孔数越多,动静刚度比越小。     

Influence of clay on the vulcanization kinetics of fluoroelastomer nanocomposites

The vulcanization kinetics of gum and montmorillonite (Na-MMT) clay filled fluoroelatomer (FKM) nanocomposite was studied using both oscillating disc rheometer and differential scanning calorimetry under isothermal and dynamic conditions. The X-ray diffraction pattern of clay filled FKM showed a shift in d-spacing toward higher values indicating the formation of intercalated silicate layer. The cure characterization showed higher rate and state of vulcanization of modified clay filled compound than that of gum and unmodified clay filled FKM indicating the accelerating effect of quaternary ammonium salt modified clay. Although the unmodified clay slowed down the cure reaction, there was marked increase in cure rate at higher level of curative. Higher loading of clay decreased the cure rate with lowering of maximum torque values. The presence of organoclay increased the torque value through the formation of confined elastomer network within the silicate galleries. The experimental data obtained provided the evidence that the curing behavior illustrated autocatalytic characteristics. The kinetic parameters determined from the model equation had good agreement with the experimental results. The calculated activation energy of the gum and clay filled systems indicated the ease of cure process with respect to the type of clay. The cure kinetics measured by different methods was well correlated with each other.     

Mooney scorch time and cure index of epoxidized natural rubber in presence of sodium carbonate

The effect of sodium carbonate on the Mooney scorch time and cure index of epoxidized natural rubber (ENR 50) was studied with concentrations of 0–2 phr and 100–160°C temperatures. A conventional vulcanization system based on an ASTM formulation was used throughout the investigation on the gum and carbon black filled rubber compound. The results indicated that the scorch time and cure index for the gum and filled compounds increased to a maximum value at 0.15 phr of sodium carbonate, and further loading of sodium carbonate caused it to decrease. This observation was attributed to the neutralization of the residual acid in ENR 50 in the initial stage, thus reducing the formation of ether crosslinks via an acid‐catalyzed ring‐opening reaction with the epoxide group in ENR 50. However, as the sodium carbonate was increased beyond 0.15 phr, the excess sodium carbonate enhanced the vulcanization rate as shown by the drop of the scorch time and cure index. The peak maximum was more evident at lower temperature and its peak height decreased with increasing temperature, suggesting that the neutralization effect by sodium carbonate was overshadowed by the faster cure rate resulting from the availability of thermal energy to overcome the activation energy of vulcanization as the temperature was elevated. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1352–1355, 2001     

Cure index and activation energy of vulcanization of natural rubber and epoxidized natural rubber vulcanized in the presence of antioxidants

The cure index and apparent activation energy of vulcanization of one grade of natural rubber (SMR L) and two grades of epoxidized natural rubbers (ENR 25 and ENR 50) were studied in the presence of three types of antioxidants [viz., 2,2′methylene‐bis(4‐methyl‐6‐tertbutylphenol) (AO 2246), poly‐2,2,4‐trimethyl‐1,2‐dihydroquinoline (TMQ), and N‐isopropyl‐N′‐phenyl‐p‐phenylenediamine (IPPD)] in the temperature range of 120–180°C by using a Monsanto automatic Mooney viscometer. Accelerated sulfur vulcanization system and up to 5 phr of antioxidant concentration was used throughout the investigation. Results indicate that both cure index and apparent activation energy of vulcanization are dependent on the type and concentration of the antioxidant used. AO 2246 (a phenol‐based antioxidant) would retard vulcanization as reflected by the higher cure index and activation energy, an observation which is attributed to the solvation and steric hindrance effects of the antioxidant. On the contrary, both TMQ and IPPD (amine‐based antioxidants) exhibit reverse behavior due to the catalytic effect of the antioxidants in generating more active sulfurating agents for vulcanization. In all cases, SMR L gives higher cure index and apparent activation energy than the corresponding ENR, a phenomenon which is associated with the activation of the adjacent double bond by epoxide group in the latter. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 3234–3238, 2000     

Structure and Properties of Radiation Cross-Linked Polypropylene Foam

Polypropylene (PP) sheets obtained through a two-step process (masterbatch method) were crosslinked by electron beam irradiation. The crosslinked PP sheets were foamed in an oven under different processing conditions. The effects of foaming temperature and time on the mechanical properties and cell structure of PP foams were studied. With the foaming temperature increasing and foaming time lengthening, both the compression modulus and compression strength dropped. Scanning electron microscope (SEM) was employed to study the morphology and cell structure of different samples and the related morphology parameters were acquired. The results showed there was an optimum temperature and time that produced the maximum expansion ratio or the minimum foam density. As foaming temperature or time increased, the cell size increased and the cell density decreased regularly. Excessively high foaming temperature and overly long foaming time caused the coalescence and even the collapse of the cells.     

Vulcanization of rubber. Kinetic parameters for SBR and simulations of vulcanization in a mold

Differential scanning caiorimetry (DSC) was used to characterize the vulcanization of styrene-butadiene rubber (SBR). The effect of three different fillers on the vulcanization process was also investigated. The fillers used were carbon black HAF and SRF and silica. The calculated reaction orders, activation energy, reaction energy, and preexponential factor, completed with physical properties, were used to calculate the temperature and extent of reaction inside a mold with time. The mathematical model used yields that are in fair agreement with experimental temperature measurements inside the mold.     

使用无转子硫变仪研究丁苯橡胶的硫化动力学

用硫变仪测试丁苯橡胶（SBR）的硫化曲线。丁苯橡胶的硫化过程遵循一级动力学反应,可以用方程In（MH-Mt）=B—kt来表示。计算不同硫化温度的反应速率常数。根据Arrhenius公式计算得出硫化反应活化能为88．112kJ／mol。     

Mooney scorch time of epoxidized natural rubber

The scorch property of accelerated sulfur vulcanization of three grades of expoxidized natural rubber (viz. ENR 10, ENR 25, and ENR 50) was studied by using Mooney Shearing Disk Viscometer in the temperature range of 100–180°C. Effects of accelerator types, concentration of accelerator, and carbon black on ENR 10 were also determined. Results obtained indicate a similar scorch behavior as that reported earlier for SMR L. However, some differences in the magnitude of scorch times in the temperature and concentration studies are observed between ENR and SMR L. These differences are attributed to the activation of a double bond by the adjacent epoxide group in ENR, the effect being more significant for a higher degree of epoxidation of natural rubber. In the case of ENR 50, differential scanning calorimetry measurement suggests that additional crosslink occurs via a ring-opening reaction at about 155°C. Based on first-order reaction kinetics, the apparent activation energy of vulcanization for the rubbers studied is estimated and discussed.     

天然橡胶硫化动力学研究

采用硫化仪测定了2种不同凝固工艺的天然橡胶（NR）的硫化过程,探讨了制胶工艺、配方和温度对硫化动力学参数的影响。研究结果发现,随着温度的上升,硫化速率常数迅速上升。在纯胶体系中,微生物凝固胶的活化能高于酸凝固胶。当加入炭黑后,酸凝固胶的活化能升高,而微生物凝固胶的活化能下降。